South Korea’s military has observed the preparations for a North Korean intercontinental ballistic missile test, Chang Kyung-soo, a South Korean Defense Ministry official, told lawmakers, The Associated Press reported.

[…] It was not immediately clear what sort of missile North Korea was preparing for a possible test. It first tested its new Hwasong-14 missile on July 4 and again on July 28. The second test showed the missile had a range of about 6,500 miles, which would put the western and central United States within range.

News of preparations for a possible missile test came as the South Korean Defense Ministry said the United States military would soon add four additional launchers for a missile defense system deployed in the country’s south, Yonhap reported.

North Korean officials claim that Sunday’s nuclear test was a hydrogen bomb. The credibility of that claim is uncertain, but the explosion was certainly the North’s largest to date.

North Korea even released photos of what it claimed was a miniaturized H-bomb capable of mounting to a ballistic missile.

Defense Secretary Jim Mattis said that “any threat to the United States or its territories, including Guam or our allies, will be met with a massive military response.” He added that the United States was “not looking to the total annihilation” of North Korea but that it had “many options to do so.”

South Korea’s Ministry of the Environment was also expected to give its approval Monday for the full deployment of a missile defense system operated by the United States, Yonhap reported, citing unidentified sources.

Installation of the system, known as Terminal High Altitude Area Defense, or Thaad, has been protested by residents of Seongju, the county in southern South Korea where it is based. And consumers in China, which fears the system’s radar will be used to monitor its territory and provoke a regional arms race, have boycotted products from South Korea in recent months over plans to deploy the antimissile system.

Air raid sirens blared across Japan last week when a North Korean missile soared across its mainland. Many wonder, now, what territories will be threatened by future tests.